A large variety of valves for use with vehicles' fuel tanks are known, among which are of more relevance with respect to the present invention those fitted with two or more valve assemblies, or those referred to as two stage valves.
A basic roll-over type fuel valve is disclosed in U.S. Pat. No. 5,738,132 disclosing a roll over vent valve comprising: a housing having a fluid inlet and a fluid outlet, the latter comprising a substantially elongated slit-like outlet aperture of the housing bounded by a valve seating. There is furthermore provided a float member located in the housing and axially displaceable within the housing between the inlet and the outlet; an elongated flexible closure membrane strip anchored at one end thereof to an end of the float member adjacent the outlet and at a portion thereof offset with respect to the outlet; spring biasing means located within the housing and bearing on the float member so as to spring bias it in the direction of the outlet; whereby the spring biasing together with buoyancy forces acting on the float member tend to press the membrane strip into sealing engagement with the outlet aperture whilst gravity forces acting on the float member tend to displace the float member away from the outlet so as to progressively detach the strip from sealing engagement with the outlet.
For example, U.S. Pat. No. 7,207,347 t discloses an over filling interdiction, vapor venting and roll over multi-function valve comprising a housing defining a confined space formed with one or more fluid inlets to said confined space, a fluid outlet chamber at top end of said housing and being in flow communication with an outlet duct; a first outlet port extending between said confined space and said fluid outlet chamber, and a second outlet port extending between said confined space and said fluid outlet chamber; a valve assembly located within the confined space and comprising a first stage float member associated with said first outlet port, and a second stage float member associated with said second outlet port, said float members being axially displaceable by buoyancy forces within the confined space about parallel axes, from an open position in which said first and second outlet port is open to a closed position; in which said first and said second outlet port is respectively sealingly engaged by said first stage float member and by said second stage float member wherein said first stage float member at least partially overlaps over said second stage float member such that when said first stage float member is in its open position it is supported by the second stage float member, the arrangement being such that only displacement of the second stage float member from the open position into closed position the first stage float member can be displaced into its closed position and sealingly engage the first outlet port.
Yet another example of a multi sage float type-valve is disclosed in U.S. Pat. No. 6,701,952 directed to a valve fitted within a fluid tank, the valve comprising a housing fitted with one or more fluid inlet ports, and an outlet port, said housing accommodating a float-type valve member axially aligned within the housing, and is displaceable therealong between an open position in which the outlet port is open, and a closed position in which the outlet port is sealingly closed; the valve characterized in that the housing is integrally formed with a nozzle member, said nozzle member being in flow communication with the outlet port and having a main portion with an outlet thereof extending within the tank; said outlet port being formed in an upper portion of the housing, said upper portion having an upper end wall and said outlet port being defined by an aperture within the upper end wall said aperture being sloped with respect to the longitudinal axis of the valve, a top wall portion of the float-type valve member facing said aperture and being equally sloped with respect to the longitudinal axis of the valve, said top wall portion of the valve member being provided with a closure membrane strip that is capable to sealingly engage the aperture within the upper end wall and to fully close the valve when the top wall portion of the float-type valve member approaches said outlet port